We are studying the structures of collagen and other related structural proteins as found in premammalian systems. Specifically, most of this work deals with shark fin elastoidin and collagen derived from gorgonian corals. This research combines X-ray diffraction, biochemistry, and electron microscopy. We have isolated and purified collagen from elastoidin and are in the process of characterizing the chain composition and cross-linking patterns. We will study the fibrillar structure of collagen from elastoidin and compare it with mammalian collagen. We have been manipulating the structures (both longitudinal and lateral) of the elastoidin by treatment with various reagents. Several of these treatments lead directly to X-ray diffraction patterns in which the longitudinal orientation no longer appears on the meridan. By measuring the intensities of the resulting small angle patterns, and deriving the appropriate electron density profiles, we will be able to identify the regions of the molecule in which binding occurs, and in which the water is readily removable. We will shortly begin experiments in which we will isolate and purify the collagen from gorgorian corals. These corals give an anamolous small angle spacing. We will compare the structure of these collagens with vertebral collagens. This will provide information on the chemical forces giving rise to the typical collagen structure.